Lecture 14: Non-SHA256 Proof-of-Work

Non-SHA256 Proof-of-Work
- Progress-freeness
- ASIC-resistant (not ASIC-proof) puzzles
- Memory-hard puzzles (e.g. Scrypt)
- Proof-of-useful-work
- Non-outsourceable Puzzles

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My notes: * Proof-of-work relies on the hash puzzle (Mining) * Mining requires specialized hardware * Can we make proof-of-work algorithm that doesn’t require expensive hardware? Yes, memory-hard puzzles and memory-bound puzzles * Memory-hard: requires a lot of memory to be calculated (ex: million x million array) * Memory-bound: requires a more of memory access over memory capacity * For ASIC resistance, we want memory-bound and memory-bound puzzles * Sha-256 is neither memory-hard nor memory-bound * Scrypt (pronounced “ess-crypt”) and Cuckoo Cycle are hashing algorithms that are memory-dependant and non-trivial to calculate * Primecoin is a cryptocurrency that makes something “useful” with its PoW algorithm which is finding Cunningham Chains of Prime Numbers * Mining Pools tend to lead to centralization * There are Nonoutsourceable puzzles in the literature that disincentivize pools but none has been implemented